The investigations are constructed around one concept, now well established, that the pacesetter potential acts as a local controller of gastric and small bowel contractions. We propose to induce duodenal-gastric reflux by creation of an abnormal pacemaker in the distal duodenum and to induce gastric retention by an abnormal pacemaker in the gastric antrum. The effects of chronic pyloric reflux and gastric retention on the gastric mucosa will be tested, particularly for barrier breaking. The motor and transit consequences of removal of the frequency gradient of the small bowel will be determined. In all of the studies, chronic electrical pacing of the pacesetter potential will be used. By-products of the researches should be insights into the role of duodenal-gastric reflux and gastric retention in the pathogenesis of gastric ulcer and an estimate of the feasibility of chronic implantation of electrical pacemakers in the stomach and small bowel of patients.